The present invention is in the technical field of elevators. More particularly, the present invention is in the technical field of elevator performance analysis.
Elevators are among the most frequently and widely used modes of public transportation in developed countries. People rely on them as a convenience to quickly travel between floors in multi-story buildings. More importantly, elevators are essential to the existence of high-rise buildings. Elevators are also essential to transport people with certain physical disabilities within multi-story buildings.
Due to their critical importance, elevators must be safe, comfortable, and reliable. Elevator inspectors, consultants, and mechanics are employed to this end. To help ensure safety, The American Society of Mechanical Engineers (ASME) developed a “Safety Code for Elevators and Escalators”, which is widely known within the elevator industry in the United States as ASME 17.1. This code establishes standard practices for the design, construction, installation, and operation of elevators and escalators. It is the responsibility of each state in the United States to establish laws regarding elevator safety. Most states do this by requiring that some or all of ASME 17.1 be followed within their state. To enforce the code, licensed elevator inspectors inspect every elevator according to a schedule specified by the state. While most of ASME 17.1 deals with other issues, portions of the code do cover the performance parameters of acceleration, speed, jerk, vibration, duty cycle, and door times, and an inspector may need to measure these parameters.
The National Elevator Industry, Inc. (NEII) publishes a document that specifies the criteria that are used to measure the performance of elevators. This document lists 50 criteria that are used by the industry for new and old elevators alike, some of which can be measured with instruments and others that are currently determined manually.
Elevators are complicated, specialized, and vary considerably from one to another. As a result, architects, building owners, and building managers often require the services of expert elevator consultants to assist with the design and management of their elevator systems. Elevator consultants frequently need to measure and analyze parameters of elevator performance, for example, to determine if an elevator is installed correctly or is being maintained correctly.
Elevator mechanics or technicians perform regular maintenance to keep an elevator operating safely and reliably. They also repair defective components, and install new elevator systems and components. During the course of these activities, they have a need to measure and analyze elevator performance parameters. For example, if passengers complain that the elevator “slips” during travel, the mechanic may measure the acceleration to determine when the problem occurs during the trip and its magnitude. As another example, the mechanic needs to measure and adjust the speed to meet specifications when the elevator is installed, and needs to repeat the procedure periodically throughout the life of the elevator.
Unlike mechanics, consultants and inspectors often do not have specific knowledge of, or access to, the elevator controller and mechanisms. In some cases, building owners themselves want to evaluate the performance of their elevators.
The parameters of elevator performance are well known but often difficult to measure. Those that are relevant to the current invention are: acceleration/deceleration, speed, jerk, vibration, trips, landings, door times, and duty cycle.
Acceleration is the rate at which the speed (velocity) of the elevator car changes over time. When the elevator car moves up to a higher landing, there is a positive acceleration as its speed (velocity) increases in the upward direction, followed by a negative acceleration (deceleration) as its speed decreases until the car is stopped. Acceleration exerts a force on the mechanical components of the elevator car and on passengers. If acceleration (or deceleration) is too great, passengers can experience discomfort or injury, and the elevator itself can be damaged. If acceleration is too low, passengers will perceive that the elevator is slow. Acceleration is measured with a device called an accelerometer. Accelerometers are widely available in many form factors and price ranges.
Speed is the distance traveled per unit of time. Buildings are designed with enough elevators traveling at sufficient speeds to guarantee minimal wait times during the busiest times. If the elevators do not meet their speed requirements, passenger wait times will become unacceptably long. Elevator speeds have traditionally been measured by a mechanic riding on top of the car while holding a tachometer against the guide rail. This is a dangerous procedure. More recently, devices have been developed that compute speed by taking the integral of the acceleration.
Jerk is the rate of change, or derivative, of acceleration. It is a factor in determining the comfort, or quality, of the ride for the elevator passenger. A “smooth” ride has low jerk. A ride with high jerk is uncomfortable, and may induce fear in passengers. Jerk is computed as the derivative of acceleration.
Vibration is oscillation about an equilibrium point. Along with jerk, it is a factor in determining the quality of the ride for the elevator passengers. Excessive vibration can cause passengers to complain of “swaying”, “shaking”, or “buzzing”. Vibration is computed as the difference between the maximum and minimum acceleration values of the oscillating acceleration value. Because vibration can occur in three dimensions, a three-axis accelerometer is used, and vibration is computed along the three axes.
Landings are the vertical stopping positions of the elevator car. Recording the pattern of landings serviced over a period of time, such as “rush hour”, or during an entire day, is necessary when analyzing traffic to determine if the elevators in a building are sufficient to meet the needs of passengers. Knowing the landing in conjunction with other parameters can help in identifying problems. For example, excessive vibration at an upper landing can mean that a hydraulic elevator is low on fluid. Landings are usually recorded manually by the person doing the testing.
A trip is the movement of the elevator car from one landing to another. Knowing the total number of trips per day is useful when setting maintenance schedules. The number of trips during busy times, and the number of trips to each landing, is useful when planning replacement or modernization of elevators. Trips can be tallied by a person riding in the car. They can be tallied automatically by recognizing computationally the start and end of a trip, such as by a pair of opposite accelerations.
Timing of the elevator car door is important. The ideal is a door that opens and closes quickly, and remains open no longer than necessary. At the same time, the door should not move so fast that passengers perceive it to be dangerous. To optimize the door motion, several door-related time periods need to be measured and adjusted. These are: 1) car stop until door starts to open; 2) door starts to open until door fully open; 3) door fully open until door starts to close; 4) door starts to close until door completely closed; 5) door completely closed until car begins to move. Door times are usually recorded by a person using a stop watch. Recently, sensors that determine the door positions have been used to automatically record door times.
The duty cycle is the percent of time the elevator car is moving relative to total time of operation. This is used to determine maintenance frequency. The duty cycle of elevators is typically estimated based upon expected traffic. Duty cycle is also a safety criteria specified in ASME 17.1.
The current methods that are used for gathering and analyzing these performance parameters all have drawbacks. Any method that requires a person to observe and record is subject to human error. Several existing tools can automatically record and analyze some of these parameters. Many of them are expensive, or are intended for permanent installation on a single elevator. Many are large and heavy systems. Some require electrical connection to the elevator controller or other electrical components which are not easily accessible. Many are very limited in the amount of data they can store. With performance parameters, recording only a few measurements is insufficient, as the values can vary considerably. Many measurements must be recorded and analyzed for accuracy.
There are many examples of systems that monitor the operation and performance of elevators that are connected to or integrated into the elevator control system.
The following patents cover systems that are connected to the controller and use test patterns for diagnostic and control purposes:
U.S. Pat. No. 4,002,973 discloses an elevator testing system. This is a removable system connected to the controller that sends a sequence of simulated signals that test the operation of the elevator. The behavior resulting from these signals is used to evaluate the elevator operation.
U.S. Pat. No. 4,330,838 discloses an elevator test operation apparatus. The apparatus uses a copy of the controller's program to provide simulated signals to the elevator. These signals are then used to tune the elevator, including the operation of the doors.
U.S. Pat. No. 4,458,788 discloses an analyzer apparatus for evaluating the performance of a number of elevators. The apparatus connects to the controller and counts the signals from components, such as call buttons and relays. These counts are compared to those of normal elevator operation
U.S. Pat. No. 5,042,621 discloses a method and apparatus for the measurement and tuning of an elevator system. The method uses simulated components to provide signals for setting up partially installed elevators.
U.S. Pat. No. 5,257,176 discloses an apparatus for setting the control operation specifications for an elevator. The system gets the control parameters from the control and displays them to the user. The user can then change the parameters remotely.
U.S. Pat. No. 7,222,698 discloses an elevator arrangement for testing the brakes on an elevator. On demand, the elevator is started moving upward, the brakes are engaged, and the torque of the motor is measured. The time it takes for the torque to reach zero is indicative of the condition of the brakes.
U.S. patent application No. 2012/0055741 discloses a system and method for monitoring and controlling multiple elevators based on patterns. This is a supervisory system that interfaces to multiple elevator controllers and copies the same control pattern to each. Elevators are then monitored for deviations from the pattern to indicate possible changes to the control patterns.
The following patents cover systems connected to the controller that use the control's internal states for diagnostic and control purposes:
U.S. Pat. No. 4,418,795 discloses an elevator servicing method and apparatus. Electrical leads are connected to the control system to monitor signals. These signals are compared to the internal states of the control, and any abnormalities are recorded and reported.
U.S. Pat. No. 4,930,604 and European Pat. No. EP0367388 disclose an elevator diagnostic monitoring apparatus. The apparatus is connected to the outputs of the elevator controller and compares signals and states to known good operation.
U.S. Pat. No. 5,760,350 discloses a method for monitoring of elevator door performance. A hardware device connected to the door operator control of an elevator determines the state of the door. The device maintains a state machine and compares the actual signals to those of the state machine. The performance of the door is analyzed and reported.
The following patents cover systems connected to the controller that monitor internal signals for diagnostic and control purposes:
U.S. Pat. No. 3,781,901 discloses a method for evaluating elevator performance by recording the analog signal from a multi-turn potentiometer on the elevator motor's shaft. This is interpreted as the position of the elevator.
U.S. Pat. No. 4,512,442 discloses methods and apparatus for improving the servicing of an elevator system. The apparatus counts faults of the elevator controller, compares these to thresholds, and places service requests based on the results.
U.S. Pat. No. 4,697,243 discloses a method for servicing an elevator system remotely. Information from the controller is retrieved over communication means. An expert system is used to make inferences about the condition of the elevator for untrained personnel.
U.S. Pat. No. 5,027,299 discloses an apparatus for testing the operation of system components of an elevator by monitoring signals associated with hall and car calls. The system determines the correct operation of the elevator and incorporates the results in the controller program.
U.S. Pat. No. 5,431,252 discloses a method for digital recording and graphic presentation of the combined performances of elevator cars. Tachometer digital signals are captured from the elevator's motor and analyzed to produce a digital display of the elevator's position.
U.S. Pat. No. 5,787,020 discloses a procedure and an apparatus for analyzing elevator operation. The apparatus connects to the controllers of multiple elevators and determines the operational functions of each elevator. These are combined to create a normal sequence of signals, and elevators deviating from the norm are identified for potential maintenance.
U.S. Pat. No. 5,817,994 discloses a remote fail-safe control for an elevator. The remote control arrangement includes a wireless transmitter and a wireless receiver that that is connected to the elevator controller for the purpose of placing calls. It can be detached when not needed.
U.S. Pat. No. 6,330,935 discloses a maintenance method for elevators that schedules maintenance for components based on their usage. Signals from components and sensors in the elevator can be used to update the schedule for their maintenance automatically.
U.S. Pat. No. 6,604,611 discloses a condition-based, auto-thresholded elevator maintenance system. Based on statistics, the system generates variable thresholds for acceptable number of faults. Maintenance recommendation can then be issued.
U.S. Pat. No. 7,699,142 discloses a diagnostic system having a user-defined sequence logic map to monitor an elevator. The apparatus connects to the inputs and outputs of the control system. The user can define logic patterns of the control signals to identify abnormalities.
U.S. Pat. No. 7,712,587 discloses a system for monitoring elevators by using a virtual elevator group. Information from individual elevators which are distributed geographically is combined into a virtual elevator group to simplify maintenance scheduling. Landing information is tracked.
U.S. Pat. No. 7,793,762 discloses a destination entry passenger interface with multiple functions. This is a terminal for user entry to determine the best car for the trip. The system gets door times from the controller to help with the dispatch.
U.S. Pat. No. 8,028,807 discloses a system to remotely record maintenance operations for an elevator or escalator. The system retrieves information about the operation and status of the elevator from the controller to determine if a maintenance technician is working on site.
U.S. Pat. No. 8,123,003 discloses a method of determining the position of an elevator car using magnetic areas of opposite poles in the hoistway. The system determines the landing number and location using RFID tags. Magnet strips are then used for fine positioning at the landing.
U.S. Pat. No. 8,307,953 discloses a system and method of determining a position of an elevator car in an elevator shaft. A series of photo detectors along the inside of the hoistway receive a light signal from the elevator car. Resistors between the detectors are used to determine the floor landing location.
U.S. Pat. No. 8,418,815 discloses a system for remotely observing an elevator system. The system monitors the sounds inside of an elevator car. The sounds can be indicative of the status of the elevator. Sounds can be reproduced from recordings remotely.
U.S. Pat. No. 8,807,248 discloses an elevator with a monitoring system in which diagnostic information is captured from multiple microprocessors in each car. One microprocessor is used to receive controller commands, while the other monitors RFID tags and sends floor information back to the controller.
U.S. Pat. No. 8,893,858 discloses a method and system for determining the safety of an elevator. The system uses an accelerometer, a microphone, and an optional smoke detector. Measurements are compared to limits to determine if the elevator is running safely. Alarms are issued as necessary.
U.S. Pat. No. 9,033,114 discloses a method of determining the position of an elevator car by using an accelerometer. The distance traveled is calculated from the acceleration. To compensate for inaccuracies in the accelerometer, additional sensors in the hoistway are needed to calibrate the accelerometer for the location of landings.
U.S. patent application No 2015/0014098 discloses a method and control device for monitoring the movement of an elevator car. The system uses multiple speed and acceleration sensors mounted on the rollers of an elevator car to determine if the car speed is exceeding limits. The multiple sensors are used to redundantly check each other to determine the probability of a fault.
Using accelerometers in portable systems to determine certain elevator performance criteria has been common for many years. These devices address 11 of the 50 criteria specified by the NEII.
Korean Pat. No. KR20040106077 discloses a portable elevator performance analyzer. This device uses an accelerometer to measure vibration and sound in an elevator car. Performance parameters associated with acceleration are displayed.
U.S. Pat. No. 5,522,480 discloses a measurement pick-up to detect physical characteristics of a lift. This is a portable device with an acceleration transducer, a timer, and memory. It is used to test the emergency stop mechanism of an elevator, checking for excessive deceleration.
U.S. Pat. No. 7,004,289 discloses an elevator performance measuring device and method. The elevator performance meter is a portable instrument containing an accelerometer for measuring properties of the vertical movement of an elevator. It specifically measures velocity, acceleration, jerk and run duration as an elevator moves. It must be manually started and stopped by the user. Memory is limited to two trips
Korean Pat. No. KR100758152 (B1) discloses a fault diagnosis method using analysis of vibration. The system uses statistics concerning ride quality and vibration to determine the probability of a fault in the elevator bearings.
The EVA-625 Elevator Vibration Analysis system from Physical Measurement Technologies, Inc. combines a three axis accelerometer in a single package with a computer processor, memory, storage, display, and battery. It measures acceleration and computes speed, jerk, and vibration. Its primary drawback is that it can record only 700 seconds of data. It is also a sizable system, in a 10.7″×9.7″×5.0″ case, weighing 9.5 lbs.
The Liftpc® Mobile Diagnosis system from Henning GMBH, similar to the EVA-265, uses a three axis accelerometer to measure and analyze vibration and ride quality. It is used in conjunction with a laptop computer or portable terminal device to store its data. It must be manually started and stopped by the user.
Measuring the operation of the doors is important to the evaluation of elevator performance. Door measurements account for 24 of the 50 criteria specified by NEII. This is often difficult to perform without access to the elevator control.
U.S. Pat. No. 8,678,143 discloses an elevator installation using an accelerometer mounted on an elevator door to measure performance properties of the door. The single accelerometer is also used to measure the same vertical properties as the aforementioned accelerometer-based systems.
Some of the more difficult measurements to get concern the time to travel between landings in an elevator. These account for 4 of the 50 NEII criteria. This is often performed manually. Determining which landing the elevator is on without access to the elevator control relies on a combination of door, speed, and distance measurements. These measurements in isolation are prone to inaccuracies.
The QarVision Remote Elevator Diagnostic System by Qameleon Technology, Inc. uses an altimeter to independently determine the position of the elevator in the hoistway. It also uses an accelerometer and independent door sensors to compute the aforementioned performance measures. QarVision is a movable system, but not a portable one. QarVision includes a self-contained computer processor and memory resulting in a high cost. The primary drawback of QarVision is that it must be installed by elevator mechanics, preventing the use by elevator inspectors, consultants, and building owners.
The need exists for a system to measure elevator performance parameters that is small, lightweight, and inexpensive; can be installed inside the elevator car by inspectors and consultants without special access to the elevator system and without special tools; automatically measures, computes, and records the performance parameters for a very long period of time; and allows the user to recall, display, graph, and prepare reports of the elevator performance. The Elevator Inspection Apparatus With Separate Computing Device And Sensors described herein addresses these needs.